JAMA : the journal of the American Medical Association
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Comparative Study
Comparison of 2 methods for calculating adjusted survival curves from proportional hazards models.
Adjusted survival curves are often presented in medical research articles. The most commonly used method for calculating such curves is the mean of covariates method, in which average values of covariates are entered into a proportional hazards regression equation. Use of this method is widespread despite published concerns regarding the validity of resulting curves. ⋯ Misleading adjusted survival curves resulted from using the mean of covariates method of analysis for our data. We recommend using the corrected group prognosis method for calculating risk-adjusted curves.
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Practice guidelines need to be up-to-date to be useful to clinicians. No published methods are available for assessing whether existing practice guidelines are still valid, nor does any empirical information exist regarding how often such assessments need to be made. ⋯ More than three quarters of the AHRQ guidelines need updating. As a general rule, guidelines should be reassessed for validity every 3 years.
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Comparative Study
Racial disparity in influenza vaccination: does managed care narrow the gap between African Americans and whites?
Substantial racial disparities exist in use of some health services. Whether managed care could reduce racial disparities in the use of preventive services is not known. ⋯ Managed care is associated with higher rates of influenza vaccination for both whites and African Americans, but racial disparity in vaccination is not reduced in managed care. Our results suggest that additional efforts are needed to adequately address this disparity.
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Multicenter Study
Mid-trimester endovaginal sonography in women at high risk for spontaneous preterm birth.
Although shortened cervical length has been consistently associated with spontaneous preterm birth, it is not known when in gestation this risk factor becomes apparent. ⋯ Cervical length assessed by endovaginal sonography between 16 weeks' and 18 weeks 6 days' gestation, augmented by serial evaluations, predicts spontaneous preterm birth before 35 weeks' gestation in high-risk women.